Hot reload doesn't refresh app when using app module import

[adhami3310]

Discussed in https://github.com/orgs/reflex-dev/discussions/5329

^{Originally posted by jgutierrez2 May 22, 2025}
Anyone else having trouble with hot reloading on .py file changes?

It's always worked great but over the last few weeks, across a few versions (including the recent 0.7.12), saving changes to a .py file will trigger a compile and refresh the browser page, but changes I've made to the UI are not reflected. Exiting and re-running "reflex run" is the only way I've been able to get changes reflected.

[linear]

ENG-6003 Hot reload doesn't refresh app when using app module import

[nengelmann]

@adhami3310 thanks for bringing this up.

I still see this behavior in reflex 0.7.14.

[adhami3310]

just wondering, do you have node installed globally? and if you don't, does it get fixed if you install it?

we also have a 0.8.0 prerelease with react router instead of next, if you can check if your original setup (before installing node globally) works or not that would be appreciated!

[nengelmann]

Yes node is installed globally with nvm.
I checked different node versions (20,21,22) with the same behavior.

I just got it working by using uvicorn>=0.25.0 in my pyproject.toml dependencies.

dependencies = [
    "reflex>=0.7.0",
    "uvicorn>=0.25.0",     # ← NEW
    "httpx>=0.27.0",
    "supabase>=2.15.2",
]

Now hot reload works just fine!

May this information is of help for you.
Thanks for your quick response.

[adhami3310]

we don't use uvicorn unless you have gunicorn also installed so that would be a tad surprising, you can test using granian or not using granian (so using uvicorn) with REFLEX_USE_GRANIAN=1 (or 0)

edit: i misspelled the env var (I'm on my phone so blame google keyboard)

[nengelmann]

I have gunicorn installed as well.

When using with env var REFLEX_USE_GRANIAN=1 my setup fails (no hot reload).

───────────────────────────────────────────────────────────────────────────────────────────── App Running ──────────────────────────────────────────────────────────────────────────────────────────────
App running at: http://localhost:3000
Backend running at: http://0.0.0.0:8000
[07:35:26] Compiling: ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 100% 26/26 0:00:00

With env var REFLEX_USE_GRANIAN=0 hot reload works fine.

───────────────────────────────────────────────────────────────────────────────────────────── App Running ──────────────────────────────────────────────────────────────────────────────────────────────
App running at: http://localhost:3000
Backend running at: http://0.0.0.0:8000
WARNING:  WatchFiles detected changes in 'app/login_page.py'. Reloading...
[07:34:50] Compiling: ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 100% 26/26 0:00:00

Does this help you?
From my side, it works just fine now.

[adhami3310]

that's a bit useful, if you run with granian and loglevel debug, do you notice anything interesting? do you see reload paths there?

[nengelmann]

Here is the part of the debug log if I do a change in the frontend code.

[INFO] Changes detected, reloading workers..
[INFO] Modified: /full/path/to/my/app/login_page.py
[INFO] Stopping worker-1 runtime-1
[INFO] Stopping worker-1
[INFO] Spawning worker-1 with PID: 1236066
[07:50:08] Compiling: ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━   0%  0/26 0:00:00Debug: Evaluating page: index
Debug: Evaluating page: personen
Debug: Evaluating page: gebaeude
Debug: Evaluating page: zeitplaene
Debug: Evaluating page: zugaenge
Debug: Evaluating page: einstellungen
Debug: Evaluating page: 404
[07:50:08] Compiling: ━━━━━━━━━╺━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━  23%  6/26 0:00:00Debug: Slowest pages:
index: 51.4ms
gebaeude: 10.8ms
zeitplaene: 10.3ms
einstellungen: 10.2ms
personen: 9.6ms
zugaenge: 7.7ms
404: 0.7ms
Debug: [timing] Evaluate Pages (Frontend): 0.11s
[07:50:08] Compiling: ━━━━━━━━━━━━━━━╺━━━━━━━━━━━━━━━━━━━━━━━━  38% 10/26 0:00:00Debug: [timing] Auto-memoize StatefulComponents: 0.13s
Debug: [timing] Copy assets: 0.00s
[07:50:08] Compiling: ━━━━━━━━━━━━━━━━━━━━╺━━━━━━━━━━━━━━━━━━━  50% 13/26 0:00:00Debug: [timing] Compile to Javascript: 0.06s
[07:50:08] Compiling: ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 100% 26/26 0:00:00
Debug: [timing] Install Frontend Packages: 0.00s
Debug: [timing] Write to Disk: 0.00s
[INFO] Started worker-1
[INFO] Started worker-1 runtime-1
Debug: 
Debug: 
Debug: Source path: /full/path/to/my/.web/styles/__reflex_global_styles.css
Debug: Setting up new context...
Debug: Finding changed files: 1.44ms
Debug: Reading changed files: 22.866ms
Debug: Sorting candidates: 1.849ms
Debug: Generate rules: 13.317ms
Debug: Build stylesheet: 0.482ms
Debug: Potential classes:  2194
Debug: Active contexts:  1
Debug: JIT TOTAL: 293.398ms
Debug: 
Debug: 
Debug: 
Debug: 
Debug: Source path: /full/path/to/my/.web/styles/__reflex_global_styles.css
Debug: Finding changed files: 1.401ms
Debug: Reading changed files: 0.068ms
Debug: Sorting candidates: 0.007ms
Debug: Generate rules: 0.05ms
Debug: Build stylesheet: 0.003ms
Debug: Potential classes:  1
Debug: Active contexts:  1
Debug: JIT TOTAL: 146.345ms
Debug: 
Debug: 
Debug:  ✓ Compiled in 1574ms (837 modules)

I don't see anything wired.
It seems to detect changes and compiles.

The major difference, as you saw in the previous comment is:

WARNING:  WatchFiles detected changes in 'app/login_page.py'. Reloading...

which does not appear when using REFLEX_USE_GRANIAN=1.

[adhami3310]

wait so in hot reload (and granian), reflex (or to be more accurate, watchfiles that's used by granian) detects the change, compiles, writes to disk, and it seems nextjs kinda picks it up? but the changes don't affect anything?

i actually think this is a different issue, it maybe that your app is imported prior to when it's I'm supposed to be, can you do traceback.print_stack at the start of your main app file and report the first few calls to it? (im an ideal situation, reflex run would only call it twice, one for initial compile and one for backend worker, then once per hot reload)

[nengelmann]

wait so in hot reload (and granian), reflex (or to be more accurate, watchfiles that's used by granian) detects the change, compiles, writes to disk, and it seems nextjs kinda picks it up?

As far as I understand, yes.
In hot reload (--env dev) and granian (REFLEX_USE_GRANIAN=1) changes are detected ([INFO] Changes detected, reloading workers..) and compiling ([07:50:08] Compiling: ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 0% 0/26). NOt sure if written to disk or .web.

but the changes don't affect anything?

Yes, in the browser the changes are not updated (I just changed a string no low level stuff).

traceback.print_stack

With hot reload and granian (REFLEX_USE_GRANIAN=1):

─────────────────────────────────────────────────────────── Starting Reflex App ───────────────────────────────────────────────────────────
  File "/full/path/to/my/.venv/bin/reflex", line 10, in <module>
    sys.exit(cli())
  File "/full/path/to/my/.venv/lib/python3.12/site-packages/click/core.py", line 1161, in __call__
    return self.main(*args, **kwargs)
  File "/full/path/to/my/.venv/lib/python3.12/site-packages/click/core.py", line 1082, in main
    rv = self.invoke(ctx)
  File "/full/path/to/my/.venv/lib/python3.12/site-packages/click/core.py", line 1697, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/full/path/to/my/.venv/lib/python3.12/site-packages/click/core.py", line 1443, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/full/path/to/my/.venv/lib/python3.12/site-packages/click/core.py", line 788, in invoke
    return __callback(*args, **kwargs)
  File "/full/path/to/my/.venv/lib/python3.12/site-packages/reflex/reflex.py", line 347, in run
    _run(
  File "/full/path/to/my/.venv/lib/python3.12/site-packages/reflex/reflex.py", line 213, in _run
    compile_future = concurrent.futures.ProcessPoolExecutor(max_workers=1).submit(
  File "/usr/lib/python3.12/concurrent/futures/process.py", line 823, in submit
    self._start_executor_manager_thread()
  File "/usr/lib/python3.12/concurrent/futures/process.py", line 762, in _start_executor_manager_thread
    self._launch_processes()
  File "/usr/lib/python3.12/concurrent/futures/process.py", line 789, in _launch_processes
    self._spawn_process()
  File "/usr/lib/python3.12/concurrent/futures/process.py", line 799, in _spawn_process
    p.start()
  File "/usr/lib/python3.12/multiprocessing/process.py", line 121, in start
    self._popen = self._Popen(self)
  File "/usr/lib/python3.12/multiprocessing/context.py", line 282, in _Popen
    return Popen(process_obj)
  File "/usr/lib/python3.12/multiprocessing/popen_fork.py", line 19, in __init__
    self._launch(process_obj)
  File "/usr/lib/python3.12/multiprocessing/popen_fork.py", line 71, in _launch
    code = process_obj._bootstrap(parent_sentinel=child_r)
  File "/usr/lib/python3.12/multiprocessing/process.py", line 314, in _bootstrap
    self.run()
  File "/usr/lib/python3.12/multiprocessing/process.py", line 108, in run
    self._target(*self._args, **self._kwargs)
  File "/usr/lib/python3.12/concurrent/futures/process.py", line 264, in _process_worker
    r = call_item.fn(*call_item.args, **call_item.kwargs)
  File "/full/path/to/my/.venv/lib/python3.12/site-packages/reflex/utils/prerequisites.py", line 545, in compile_or_validate_app
    compile_app(check_if_schema_up_to_date=check_if_schema_up_to_date)
  File "/full/path/to/my/.venv/lib/python3.12/site-packages/reflex/utils/prerequisites.py", line 481, in compile_app
    get_compiled_app(
  File "/full/path/to/my/.venv/lib/python3.12/site-packages/reflex/utils/prerequisites.py", line 457, in get_compiled_app
    app, app_module = get_and_validate_app(
  File "/full/path/to/my/.venv/lib/python3.12/site-packages/reflex/utils/prerequisites.py", line 414, in get_and_validate_app
    app_module = get_app(reload=reload)
  File "/full/path/to/my/.venv/lib/python3.12/site-packages/reflex/utils/prerequisites.py", line 375, in get_app
    __import__(module, fromlist=(constants.CompileVars.APP,))
  File "<frozen importlib._bootstrap>", line 1360, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1310, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 488, in _call_with_frames_removed
  File "<frozen importlib._bootstrap>", line 1360, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1331, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 935, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 999, in exec_module
  File "<frozen importlib._bootstrap>", line 488, in _call_with_frames_removed
  File "/full/path/to/my/app/__init__.py", line 3, in <module>
    from .app import app
  File "<frozen importlib._bootstrap>", line 1360, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1331, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 935, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 999, in exec_module
  File "<frozen importlib._bootstrap>", line 488, in _call_with_frames_removed
  File "/full/path/to/my/app/app.py", line 6, in <module>
    traceback.print_stack()
[08:23:50] Compiling: ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 100% 26/26 0:00:00
─────────────────────────────────────────────────────────────── App Running ───────────────────────────────────────────────────────────────
  File "/full/path/to/my/.venv/bin/reflex", line 10, in <module>
    sys.exit(cli())
  File "/full/path/to/my/.venv/lib/python3.12/site-packages/click/core.py", line 1161, in __call__
    return self.main(*args, **kwargs)
  File "/full/path/to/my/.venv/lib/python3.12/site-packages/click/core.py", line 1082, in main
    rv = self.invoke(ctx)
  File "/full/path/to/my/.venv/lib/python3.12/site-packages/click/core.py", line 1697, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/full/path/to/my/.venv/lib/python3.12/site-packages/click/core.py", line 1443, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/full/path/to/my/.venv/lib/python3.12/site-packages/click/core.py", line 788, in invoke
    return __callback(*args, **kwargs)
  File "/full/path/to/my/.venv/lib/python3.12/site-packages/reflex/reflex.py", line 347, in run
    _run(
  File "/full/path/to/my/.venv/lib/python3.12/site-packages/reflex/reflex.py", line 273, in _run
    backend_cmd(
  File "/full/path/to/my/.venv/lib/python3.12/site-packages/reflex/utils/exec.py", line 365, in run_backend
    run_granian_backend(host, port, loglevel)
  File "/full/path/to/my/.venv/lib/python3.12/site-packages/reflex/utils/exec.py", line 488, in run_granian_backend
    target=get_app_instance_from_file(),
  File "/full/path/to/my/.venv/lib/python3.12/site-packages/reflex/utils/exec.py", line 338, in get_app_instance_from_file
    return f"{get_app_file()}:{constants.CompileVars.APP}"
  File "/full/path/to/my/.venv/lib/python3.12/site-packages/reflex/utils/exec.py", line 321, in get_app_file
    module_spec = importlib.util.find_spec(get_app_module())
  File "<frozen importlib.util>", line 91, in find_spec
  File "<frozen importlib._bootstrap>", line 1360, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1331, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 935, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 999, in exec_module
  File "<frozen importlib._bootstrap>", line 488, in _call_with_frames_removed
  File "/full/path/to/my/app/__init__.py", line 3, in <module>
    from .app import app
  File "<frozen importlib._bootstrap>", line 1360, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1331, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 935, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 999, in exec_module
  File "<frozen importlib._bootstrap>", line 488, in _call_with_frames_removed
  File "/full/path/to/my/app/app.py", line 6, in <module>
    traceback.print_stack()
App running at: http://localhost:3000
Backend running at: http://0.0.0.0:8000

[adhami3310]

ok this is the part that's weird, i thought that find_spec doesn't load, but in your case it does! i will read on it more but that should be helpful enough

[adhami3310]

ok i see something, you have "from .app import app" and find spec would import the parent of the module, so at least as a work around in your case, you should remove that line